AN728: Remote Keyless Entry and Convenience Center Reference Design with LIN Bus Interface:  Microchip Application Note Published 26-Sep-02   (app note added 2/06)

Automatic Door Opener with PIC12c508:  This circuit can be used to operate an electric strike or an electromagnetic lock on a door. It is not  door being opened/closed, but a small electromagnetic strike which unlocks  door…. (added 4/05)

Code Lock:  The circuit described here is of an electronic combination lock for daily use. It responds only to the right sequence of four digits that are keyed in remotely. If a wrong key is touched, it resets the lock. The lock code can be set by connecting the line wires to the pads .... (electronic Circuit / Schematic added 10/04)

Combination Lock (PIC16F84):  (electronic diagram added 6/03)

Combination Lock for Car Liftgate:  (circuit / schematic design added 6/06)

Combination Lock:  This circuit is very basic to build. To open a the lock which is connected to the K1 Load. you must press each momentary switch in the correct sequence. The sequence used in this circuit is S1,S2,S3,S4. If any of the other switches are pressed the circuit will reset and you will need to start over. Depending on how you wire the switches, you can use any4 switch combination (added 2/03)

Digital Combination Lock:  (schematic / circuit design added 9/02)

Digital Electronic Lock (circuitdb):  The digital lock shown below uses 4 common logic ICs to allow controlling a relay by entering a 4 digit number on a keypad. The first 4 outputs from the CD4017 decade counter (pins 3,2,4,7) are gated...(added 03/07)

Digital Electronic Lock:  (electronic schematic / circuit added 11/05)

Electronic Card Lock System:  (electronic Circuit / Schematic added 10/04)

Electronic Combination Lock (AVR):  (circuit / schematic design added 6/06)

Electronic Combination Lock with AVR:  (electronic schematic / circuit added 2/05)

Electronic Combination Lock:  This circuit is very basic to build. To open a the lock which is connected to the K1 Load you must press each momentary switch in the correct sequence. The sequence used in this circuit is S1,S2,S3,S4. If any of the other switches are pressed the circuit will reset and you will need to start over. Depending on how you wire the switches, you can use any 4 switch combination. (added 09/05)

Electronic Safety Lock Based on Attiny26:  (electronic circuit added 4/05)

Enhanced Alarm Keypad:  (schematic / circuit design added 9/02)

Low Cost Digital Code Lock:  (electronic Circuit / Schematic added 10/04)

Programmable Digital Code Lock:  (electronic circuit added 10/05)

Remote Keyless Entry and Convenience Center Reference Design with LIN Bus Interface:  Microchip Application Note Published 26-Sep-02   (app note added 2/06)

Simple Code Lock:  (electronic Circuit / Schematic added 10/04)

Simple Low Cost Digital Code Lock:  (electronic Circuit / Schematic added 10/04)

Single Button Lock Provides High Security:  03/04/99 EDN-Design Ideas / (added 5/03) Figure 1 is the block diagram of an easily programmed, single-button combination lock. You operate the lock by using a series of short and long pulses from a momentary switch that masquerades as a doorbell button. The circuit uses inexpensive CMOS logic. The retriggerable timer, T1, locks out entries made after the T1 code-entry window, thereby greatly enhancing security. The circuit in Figure 2 operates as follows: The Schmitt-trigger quad NAND gate, IC1, debounces the code-entry switch and, with the aid of simple analog circuitry, produces separate outputs for activation times of less than and more than 0.3 sec. These outputs connect to the select gate, IC5. The initial entry also sets timer T1 to enable the decoded decade counter, IC3. Each entry clocks IC3.